Researchers estimate that between 900 million to 9 billion gallons of landfill leachate are produced annually in the United States, with an estimated 250 million gallons annually being managed in Florida. This volume of wastewater raises environmental and economic concerns, and represents an opportunity to reclaim both water and nutrients from a wastewater stream that is currently being “thrown away.”
Leachate is water is partly inherent in solid waste and partly the result of rainfall that falls on the wastes after placement in a landfill, which subsequently becomes contaminated with a variety of chemicals contained in the solid waste. Landfill leachate is characterized by heavy metals, high chemical oxygen demand (COD) and biological oxygen demand (BOD) compounds, total organic carbon (TOC), volatile organic carbons (VOC), ammonia-nitrogen, suspended solids and can contain other compounds that resist biological decomposition. Chemical constituents of leachate can be toxic or carcinogenic, and certain compounds can emit objectionable odors. Landfill leachate can also transport viruses and bacteria harmful to human health.
Leachate management methodologies became necessary in the 1980's when the US Environmental Protection Agency (EPA) and state regulatory agencies began adopting the “dry tomb” approach to landfill construction which requires new landfill cells to have bottom and top liners, as part of leachate management systems. Soon after implementing these regulations researchers began to investigate the effects of adding water or recirculating leachate to the lined cells. This research confirmed that recirculation of leachate accelerates gas production and the degradation of organic waste. This so called “wet cell” research led to the development of “bioreactor landfills” in which significant quantities of leachate are recirculated while organic waste is being degraded. Once biological activity in the cells ceases, however, bioreactor landfill operators need methods to dewater the cells and dispose of or treat the leachate.
Leachate is managed in a variety of ways including trucking or piping leachate to a wastewater treatment plant (WWTP), deep well injection with minimal treatment, evaporation, biological uptake of constituents in engineered wetlands, and various chemical treatment processes. Some facilities use more than one method. All methods of processing leachate use energy and can have negative environmental impacts. Few WWTPs are designed to treat leachate, which disrupts biological treatment in all but the smallest amounts.
An on-site treatment method that minimizes energy consumption and adverse impacts such as odors, captures the inherent macro and micro nutrients in the leachate, segregates heavy metals and VOCs, dewaters the cell, and provides reuse of the decontaminated water is therefore desirable.
Thus there is a need to address and/or overcome these deficiencies.